The present invention relates to deck support structures adapted for use in mobile platforms, and more specifically to an aircraft deck support structure for seating decks or cargo decks.
An aircraft deck design typically comprises a plurality of deck support beams which run in an inboard/outboard direction and are attached at individual frames to the aircraft. The major components of each deck support beam are an upper chord which supports deck plating, and a lower chord generally arranged in parallel with the upper chord and separated from the upper chord by a web. At selected spaced intervals along each of the deck support beams, each of a plurality of I-shaped, J-shaped, C-shaped or H-shaped beams are positioned at about 90xc2x0 angles to the deck support beams. For simplicity, the I-shaped, J-shaped, C-shaped or H-shaped beams will hereinafter be referred to as cross-support beams. In many aircraft designs, the cross-support beams are arranged in a fore/aft direction and partially support deck plating in either a passenger compartment or a cargo stowage compartment. The cross-support beams commonly have notches which receive locking rings used to lock-in and support seats in the passenger compartment or cargo container systems in the cargo stowage compartment.
In existing aircraft designs, aircraft designers used several concepts to connect the combination of the inboard/outboard running deck support beams and the cross-support beams. Each concept used to date has drawbacks. In the earliest concept, both a lower flange and web of the cross-support beam were cut to make the cross-support beam the equivalent of a pin joint at the connection to the deck support beam. The upper flange of the cross-support beam was supported by the upper chord of the deck support beam. Several drawbacks exist with this concept. By cutting the cross-support beam, its continuous moment carrying capacity is lost. To regain moment carrying capacity, hardware including brackets and fasteners were used to splice the cross-support beam to the deck support beam at each cross-support beam to deck support beam intersection. Both the time to build the deck and the weight of the deck system increase using this design.
Another concept used by aircraft designers for deck assembly required the deck support beam be cut to provide clearance for the cross-support beam. Similar to the concept of cutting the cross-support beam, hardware, including fasteners and angle brackets, are required to splice the cross-support beam to the deck support beam at each aperture location in order to regain the moment carrying capability of the deck support beam. This design also has several drawbacks. Some reinforcement of the deck support beam is normally required due to the structural strength lost at the clearance cut. Also, by requiring hardware to re-splice the beam at each intersection with a cross-support beam, the amount of time required to build the deck is increased. Moreover, the weight of the overall deck increases due to both the additional reinforcement and hardware.
In more recent aircraft designs, each cross-support beam is entirely supported on the upper surface of each deck support beam upper chord. No cuts in either the deck support beam or the cross-support beam are required. The full moment carrying capacity of both the deck support beam and the cross-support beam are developed. The drawback of this concept is that the combined vertical height of the deck support beam and cross-support beam reduces the overhead clearance (or usable compartment volume) in the particular compartment. If the deck support beam or cross-support beam vertical heights are reduced to improve overhead clearance, structural weight increases due to the reduced moment carrying capability of shallower structures.
A need therefore exists for a deck design for joining deck support beams and cross-support beams which maximizes overhead compartment space, reduces the amount of hardware required to assemble the deck system, and optimizes the moment carrying capacity of the combination of the cross-support beams and the deck support beams.
In a preferred embodiment of the present invention, a deck support beam having a discontinuous upper chord includes an aperture in the deck support beam web to provide clearance for a cross-support beam. An upper support flange of the cross-support beam spans the aperture in the upper chord of the deck support beam. A web and lower stiffening flange of the cross-support beam are suspended in the aperture of the deck support beam. The support flange of the cross-support beam structurally re-splices the upper chord of the deck support beam across the aperture using a plurality of mechanical fasteners. Only the plurality of fasteners is required to join the cross-support beam at each intersection with the deck support beam. The shape of the cross-support beam is also optimized to support the weight of the deck throughout the length of the cross-support beam by changing the geometry of the cross-support beam in each span between deck support beams.
The deck support beam of the present invention is formed by machining the desired configuration from a solid block of metal. Both an upper and a lower chord are formed having a beam web joining the upper to the lower chord. A plurality of vertical ribs are also machined into the intermediate web approximately perpendicular to the beam web. At predetermined vertical ribs one end of the rib is bifurcated, thus providing a clearance opening formed as a generally U-shaped aperture through the upper chord and a portion of the beam web of the deck support beam. Adjacent to each U-shaped aperture, either a horizontal recess or a raised surface is also machined into an outer face of the upper chord of the deck support beam.
The cross-support beams of the present invention are preferably formed as either I-shaped or J-shaped beams. Each cross-support beam includes an upper support flange formed as a wide flange to span each U-shaped aperture, and a web joining the upper support flange to a stiffening flange. The stiffening flange is narrower than the upper support flange to allow both the stiffening flange and the web to be suspended within the U-shaped aperture formed in the deck support beam. A plurality of mechanical fasteners is used to join each upper support flange of a cross-support beam to a selected horizontal recess or raised surface on the deck support beam, thereby splicing the deck support beam in the area where each U-shaped aperture is formed without requiring additional hardware such as brackets or angles.
The size and geometry of both the deck support beam and the cross-support beam of the present invention can vary depending upon the span length and the spacing of the deck support beams and the weight carried by the deck of the aircraft. The gage thickness of the chords of the deck support beam as well as the depth of the deck support beam can be varied to provide the weight and moment carrying capacity necessary for the individual deck. By varying the width of the support flange of each cross-support beam along its fore and aft length as well as varying the depth or thickness of its stiffening flange, the moment carrying capacity and weight of the cross-support beam are optimized.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.